The invention relates to a tension device for a nonskid chain having a housing, a winding reel and a ratchet allocated to the latter; the winding reel is mounted to rotate about its axis inside the housing and is prestressed in the winding direction; it has a gear rim with teeth arranged along its circumference; a tension line that can be retracted into the housing through a housing opening can be connected to the winding reel, such that in a first position, the ratchet blocks the rotational movement of the winding reel in the tension direction by engaging the ratchet in the teeth of the gear rim.
Tension devices are used with nonskid chains, in particular snow chains, to prevent unwanted unreeling of the tension line after assembly. The tension line is usually a tension cable but may also be embodied as a tension chain, for example. The tension devices considered here are used primarily on trucks or heavy vehicles but may essentially be used with any type of vehicles having wheels.
European Patent No. EP 1 935 674 A1 describes a tension device of the type defined in the introduction. A tension line that can be retracted into the housing through a housing opening is connected to a winding reel, which is prestressed in the winding direction and is mounted to rotate about its axis inside the housing. The winding reel has a gear rim, which is connected in a rotationally fixed manner and in which a ratchet engages, thereby blocking the movement of the gear rim either in the winding direction or in the opposite direction, depending on the position of the ratchet.
With these tension devices, it has been found that the nonskid chain on the vehicle wheel can result in damages when the chain is installed too tightly on the wheel. For example, when the nonskid chain migrates around the wheel—which occurs especially at higher speeds—this movement of a chain in close contact with the wheel can lead to abrasion and damage to the tire. This is the case on truck tires in particular because these problems are greatly intensified there in comparison with nonskid chains/snow chains on passenger vehicles due to the larger dimensions and greater weight of the tires and the greater load on them. On the other hand, the chain should be held with a certain force when mounted on the wheel, so that the chain sits well on the wheel and cannot slip laterally.
One object of the invention is therefore to create a tension device which will overcome the disadvantages mentioned above. In particular, a certain play should be possible in tightening the chain.